A group of farmers concerned about a proposed wind farm on the Yorke Peninsula say they aren't happy with a new deal done with aerial sprayers.

The deal, announced late last week, means that turbines would be turned off when aerial spraying was to be undertaken, in a move to ease farmers concerns. The arrangement has been signed off between the company behind the wind farm proposal and an aerial spraying company.

Naomi Bittner, chairperson of the Heartland Farmers Association, says there are aspects of the deal she's worried about, and says she would have preferred the deal be done with landholders as well.

Michael Baggart, acting project manager for the CERES windfarm project says the aerial spraying company is the most logical group to do a deal with, as they know the risks and conditions needed to spray safely.